The present invention relates to cigarettes and other smoking articles which contain a catalytic composition, preferably as part of the fuel element, that substantially decreases the amount of carbon monoxide contained in the mainstream smoke during smoking. The present invention also relates to the catalyst-containing carbonaceous fuels themselves, as well as to methods of making such carbonaceous fuels. Fuel elements which contain a catalytic composition in accordance with the present invention are especially useful in smoking articles having an aerosol generating means which is physically separate from the fuel element.
Preferred smoking articles of the present invention are capable of providing the user with the pleasures of smoking (e.g., smoke taste, feel, satisfaction, pleasure, and the like), by heating but not burning tobacco, and with reduced levels of carbon monoxide. As used herein, the term "smoking article" includes cigarettes, cigars, pipes, and the like, which use tobacco in various forms.
Cigarettes, cigars and pipes are popular forms of tobacco smoking articles. Many smoking products and smoking articles have been proposed through the years as improvements upon, or as alternatives to, these popular forms of tobacco smoking articles, particularly cigarettes.
Many, for example, have proposed tobacco substitute smoking materials. See, e.g., U.S. Pat. No. 4,079,742 to Rainer et al. Two such materials, Cytrel and NSM, were introduced in Europe in the 1970's as partial tobacco replacements, but did not realize any long-term commercial success.
Many others have proposed smoking articles, especially cigarette smoking articles, based on the generation of an aerosol or a vapor.
Recently, in European Patent Publication Nos. 0174645 and 0212234, U.S. Pat. No. 4,714,082 to Banerjee et al. and U.S. Pat. No. 4,756,318 to Shannon et al., assigned to R.J. Reynolds Tobacco Co., there are described cigarette smoking articles which are capable of providing the user with the pleasures associated with smoking, by heating but not burning tobacco and without producing appreciable quantities of incomplete combustion or pyrolysis products. One such smoking article, the Premier.TM. brand cigarette, was recently introduced in the United States by the R.J. Reynolds Tobacco Co. The mainstream smoke of that cigarette typically contains about 9 to 12 mg of carbon monoxide (CO) per cigarette. See the monograph "Chemical and Biological Studies, New Cigarette Prototypes That Heat Instead of Burn Tobacco," published by the R.J. Reynolds Tobacco Co., at pages 126-127 (hereinafter "RJR Monograph").
Several attempts have been made at using catalysts and/or other modifying methods for decreasing the levels of carbon monoxide in tobacco (or tobacco substitute) smoke. However, apparently none of these techniques has met with any substantial commercial success.
U.S. Pat. No. 4,397,321 to Stuetz proposes tobacco and non-tobacco smoking compositions which contain a catalyst composition consisting of a fine ash and a transition metal compound, especially oxides of manganese or iron. This patent also describes several previous attempts at incorporating catalysts into cigarettes to decrease levels of selected smoke constituents.
U.S. Pat. No. 4,182,348 to Seehofer et al., proposes a method for removing nitric oxide and carbon monoxide from the tobacco smoke of cigarettes by adding a ruthenium compound having a perovskite structure (M.sub.2 M'RuO.sub.6) to the cigarette.
U.S. Pat. No. 3,368,566 to Avedikian proposed a filter containing catalytic oxides, such as manganese dioxide, chromium trioxide and other oxides of chromium and copper to convert carbon monoxide to carbon dioxide.
U.S. Pat. No. 4,317,460 to Dale et al., proposes the use of microporous supported, low temperature catalysts in cigarette filters for the oxidation of carbon monoxide to carbon dioxide. Dale also refers to prior unsatisfactory attempts of Eastman Chemical Products Inc. to incorporate various oxidants and catalysts into filters to convert carbon monoxide to carbon dioxide.
U.S. Pat. No. 4,215,708 to Bron, describes a novel cigarette holder with a catalytic afterburner which is intended to convert carbon monoxide and incompletely burned hydrocarbons into acceptable smoke compounds.
Non-catalytic methods for decreasing the levels of carbon monoxide in cigarette smoke have also been attempted. See inter alia. U.S. Pat. No. 4,589,428 to Keritsis (extraction of tobacco), U.S. Pat. No. 4,142,534 to Branti (use of tobaccoless region), and U.S. Pat. No. 4,258,730 to Tuskamoto (use of magnetic field).